You know, and perhaps this goes without saying (and maybe makes it different enough not to count), but you could easily load Windows XP into a virtual machine with VMPlayer. Once I install Win8, I’m going to be creating VMs for Windows 98 SE (Buzz Tracker, and enough of an archive I want to lift things from 🙁 and Buzz is so unstable, more so on later Win versions), Windows XP and possibly Linux.
Or, if you have Win7 Ultimate, you can install a “free” copy (Ultimate comes with an XP licence) of XP Mode, in which sound works too.
I’m not entirely sure if ASIO4ALL works well, or at all, in these, but I don’t see why not, and I will surely be finding out later this year.
That would give you an XP environment that mimics real situations relatively closely (albeit not with the same hardware variety). Always good to test on a range of systems, and perhaps you already use VMs for this anyway..?